This invention relates to an LED backlight device and an LCD device having the LED backlight device.
A general LCD (Liquid Crystal Display) device is configured to irradiate an LCD panel with a light emitted by a light source, and to change alignments of liquid crystals arranged on the LCD panel so as to display an image using the light passing through the LCD panel.
The light source used in such an LCD device is called as a backlight, since the light source is disposed on a backside of the LCD panel (i.e., a side opposite to a display surface of the LCD panel). The conventional light source is composed of a cold cathode ray tube or a semiconductor light emitting element. The light source using the semiconductor light emitting element has been broadly used, since such a light source has a long lifetime and contributes to reduction of power consumption.
In this regard, there is known a conventional surface-emitting light source using an LED (Light Emitting Diode) as the above described semiconductor light emitting element, and a plate-like member called as a light guiding plate (or a light diffusion plate) for guiding the light emitted by the LED. The light emitted by the LED is incident on an end surface of the light guiding plate, and reflected and diffused in the direction perpendicular to a surface of the light guiding plate (see, Japanese Laid-Open Patent Publication No. 11-232920).
However, in the conventional backlight device, the light diffused in the light guiding plate tends to attenuate due to the reflection and diffusion, as a distance from the incident surface (i.e., the end surface of the light guiding plate) increases. Therefore, in order to obtain a high light intensity uniformly over the entire surface, the structure of the light guiding plate needs to be complicated, and the LED backlight device needs to be thick.